The present invention relates to a plant growing technique such as planting trees, and more specifically, to a technique of selectively growing young trees or the like which is resistant to ultraviolet rays so that vegetation such as a forest which is resistant to ultraviolet rays can be reliably obtained.
There has been discussed recently on the issue of ultraviolet rays problem on earth. Because especially the ozonosphere of stratosphere surrounding the earth is recently destroyed, the ultraviolet rays come to the earth from outside and has been confirmed to show bad influence on biology on the earth.
For example, as to human body, there has been reported the increment of damage due to ultraviolet rays, and it has been confirmed that the increase of skin cancer cases are due to increment of radiation by ultraviolet rays. Thus damage based on ultraviolet rays was thought to cause the occurrence of active oxygen. Niwa, one of the present inventors, has studied their pharmacological, biochemical properties on several damages caused by active oxygen for long years.
The real states that damages based on conventional ultraviolet rays are mainly by studying on their effects on human body as the main topics. In contrast to this, the present inventors has reached to the conclusion that ultraviolet rays have also given big damages on forest.
It is disclosed that the biggest reason that damage forwarded to the forest is acid rain""s exertion. For example, at Schwarzwald district in Germany, a report dealt with big damage covered large area where so many trees uprightly withered by acid rain. The acidic oxides such as sulfur-containing oxides existed in the industrial burning, were dissolved in the rain drops and resulting become acidic rain.
The investigation on the damage was performed repeatedly by the present inventors who visited the damaged domestic forest and obtained many results.
The present inventors observed the damage of the domestic forest by repeatedly visiting several places of the damaged forest in several districts. After a detailed investigation about the observed states, the present inventors investigated that it is possible that the factors other than acid rain strongly concerned with abnormal phenomena of withered trees found largely in the forest found. The damages may possibly be due to ultraviolet rays found as the main factor in relating to forest damage to our further research result.
There is not so far examined before on the effect of ultraviolet rays exerting the forest damage. As the present inventors viewed the forest damage state due to ultraviolet rays, it is necessary to take a practical measure rapidly to inhibit such forest damage. Because enlarging the depletion of ozonosphere and the ultraviolet radiation increasing of world scale, it is a top urgent action to be taken for inhibiting the damage caused by ultraviolet rays during the several factors exerting to forest damage. If the damages were dealt with no policy, in the future, the forest trees withered uprightly worldwide by the ultraviolet rays. And the prophecy is forest will be disappeared with global scale.
The object of the present invention is to suppress the damage on forest caused by ultraviolet rays.
The man-planted forest of the present invention is characterized in that is constituted by planting seedling having multiploid (TASUSBI in Japanese). The chromosome number of the seedlings is triploid or tetraploid. The seedlings are those of a conifer. The seedlings of a conifer are seedlings selected from the group consisting of Japanese cedar and Japanese cypress. The chromosome number of the seedling is obtained by increasing the number of chromosomes such as by breeding and mutation.
The method of planting trees of the present invention is characterized in that it comprises the steps of: selecting seedlings having multiploid chromosome; and planting the selected seedlings. The chromosome number of the seedlings is triploid or tetraploid. The seedlings are those of a conifer. The seedlings of a conifer are seedlings of Japanese cedar or Japanese cypress. The chromosome number of the seedlings is obtained by means of increasing the number of chromosomes such as breeding and mutation. The method of growing plants of the present invention is characterized in that it comprises the step of artificially forming vegetation which is significantly resistant to ultraviolet rays, as compared with vegetation constituted of diploid plants, by selectively growing plants whose chromosome number exceeds the basic number intrinsic of the species.
In this specification, xe2x80x9cmultiploidxe2x80x9d (TASUSEI in Japanese) means those chromosomes with more than 3-fold of fundamental chromosome by multiplying integral number of chromosome, and those chromosomes possessing more or less, by 1 to few, than the basic number is acquired by the species. Furthermore it should be noted that haploid, or diploid which is normally observed in plants, is not included into the scope defined by the aforementioned xe2x80x9cmultiploidxe2x80x9d.